In the case of certain substances put on the market in sealed containers, in particular liquids for medical purposes, or food, it is a requirement that the quantity of oxygen in the space above the filling should not exceed a certain level, since too much oxygen is harmful to the substance packed in the container. This maximum permitted quantity of oxygen is many times smaller than the quantity of oxygen contained in the atmospheric air with which the said space is filled after filling of the container.
Hitherto, for reducing this amount of oxygen, as much air as possible was extracted from the said space above the filling, so that a vacuum was created there. However, too great a vacuum may not be created there, otherwise there is a risk of the liquid with which the container is filled starting to boil and being extracted with the air and/or of the container collapsing.
The amount of air going with maximum permitted vacuum does, however, still contain an inadmissibly large quantity of oxygen. In order to make this quantity of oxygen harmless, a so-called antioxidant is added to the filling. However, there are to an increasing extent prohibitions of this last-mentioned practice.
In the French patent specification No. 1426235 a process and device of the above-mentioned type is disclosed in which the filling opening of a container is inserted in a space which is sealed off from the outside air after which said space is placed in connection with a vacuum source by opening a first valve means so that a vacuum is created inside said space and said container and then, by opening a second valve means said first valve means being closed, said space is placed in connection with a source of a chemically inert gas so that said gas flows in random directions into said container and mixes therein with the air still present in the vacuum, whereupon again a vacuum is created in said space. The valve means are formed by two valves by means of which said space can be put into communication with either a source of an inert gas or with only one vacuum source, said valves comprising each a valve disc connected to a valve rod which disc operates with an annular valve seat. In addition a third valve of this type is provided by means of which said space can be put into communication with the outside air in order to be able to remove the container from said space after the container being closed.
It has been found that according to the known process the quantity of oxygen in the space above the filling in a container can be reduced only to slightly less than 2% which percentage is much too high for containers containing a pharmaceutical product. Moreover valves of the type used in the known device cannot be cleaned to that extent as required by the pharmaceutical industry.
In the British patent specification No. 910584 a device for the evacuation and sealing of containers is described in which a nozzle is inserted into the container and the sidewalls of the container are pressed against the nozzle to form a substantially air tight seal there between. The nozzle is connected through a conduit with a passageway bored in a ring which is adapted to rotate together with said nozzle, which passageway opens at a face of said ring which is in engagement with a face of a stationary plate in which a plurality of recesses are formed which during the rotational movement of the ring become aligned successively with the opening of said passageway, each recess in the stationary plate being into communication through said plate with a separate conduit which is connected with a source of an inert gas and a vacuum source respectively.
Thus in this control mechanism for each step of either forming a vacuum or feeding an inert gas there has to be a conduit extending from the relevant recess in the fixed plate to the relevant source so that it is practically impossible to have more than three recesses resulting in that only three steps can be executed, a vacuum step, a gas feeding step and again a vacuum step. Moreover the recess for the gas feeding step is located between the two recesses for the vacuum steps so that there is the risk that the vacuum source will be in direct communication with the vacuum source through the joint between the ring and the fixed plate.
The object of the invention is to provide an improved process and dvice by which the quantity of oxygen in the space above the filling of a container can be decreased to less than 0,5%.
This object is achieved in that in the process according to the invention, the compressed gas is blown into the container in a direction running obliquely to the vertical axis of symmetry of the container.
In this way, by blowing in the inert gas also a very large quantity of the air still present in the vacuum is expelled from the container and is replaced by the inert gas, thereby considerably reducing the quantity of oxygen, in particular when the inert gas, for example nitrogen, has a lower specific gravity than air, so that an improved expelling effect is obtained.
Preferably a final vacuum is created in the space as a last step, during which step the quantity of oxygen in the container is, of course, again reduced, the final vacuum being of a depth which differs from that of the previous vacuums.